In this paper, simulation about a unique heat pump water
heater with hybrid heat source was studied. Different parameters
effects on system, where used different refrigerants,
were compared.
(1) The heating capacities, power consumption, COP of
three refrigerants presented an analogous relation during
the whole heating process with the growth of time.
When heating capacities decreased with the increased
of outlet water temperature, power consumption
increased in opposite, which resulted in COP dropping
gradually. Meanwhile, CO2 presented poor performance
due to its high presser drop. So, it is suggested to choose
appropriate structure for CO2 system pointedly.
(2) In given operating conditions, the heating capacity as
same as the power consumption for the three refrigerants
performed the same changed tendency with
a liner relationship. However, it was noted that there
were some differences of COP with the ambient temperatures.
When the ambient temperature was under
13 C, the increasing order of COP among three refrigerants
was R744 > R134a > R22. If it was over 13 C,
the order was changed to R134a > R744 > R22. Based on
the simulated data, the solar energy input ratios of R22,
R134a and R744 were changed in the range of 30%e44%,
48%e89% and 39%e73% respectively at all corresponding
outdoor temperature. In view of the purpose of
using solar energy properly, it may be necessary to
choose the right area of collecting panel.
(3) To synthesize all operating conditions, R134a is not an
applicable substitute of R22. However, R744 refrigerant
owing good thermal performance could replace freon
refrigerant. The only question is that R744 refrigerant
has extremely high pressure. So some ways should be
presented to lower its operating pressure in the future.